15m & 20m Trapped Wire Dipole Antenna

ANTENNA DESCRIPTION

The TZ-WD-1520 is a trapped wire antenna designed to permit operation on the primary DX bands of 15m & 20m. The antenna is ideal for local communications within 1000-2000 km of your location or for DX depending on how high the antenna is mounted and in what configuration. If you're new to the HF bands and want to try a bit of local ragchewing, why not experiment with this antenna first. Alternatively, when the antenna is mounted at height, and well in the clear, this antenna will permit DX contacts to be made on the 15m and especially the 20m band.

LOCAL QSOs

For local communications around your location within 1-2000km the antenna can be mounted in either a dipole or inverted vee configuration, however the Inverted Vee configuration is best suited for a high angle of radiation, providing excellent signal for interstate QSOs. For local QSOs the antenna is best mounted at a height of between 6m and 8m.

DX QSOs

For effective DX contacts the antenna should be mounted at least 15m above the ground at all points and be configured in a straight dipole configuration. At heights of 20m or greater the antenna will produce outstanding DX results on both 15m and 20m. At 30m or greater, DXCC on the these bands will only be limited by your own commitment to being there when the DX is! As the sunspot cycle improves, DXCC with 100w will be easily achievable using this antenna.

BLOCK SIZE & MOUNTING CONSIDERATIONS

For the amateur without much room, or dollars, or who has an XYL not keen on a big antenna and tower in the back yard, this can be a real opportunity. The wire and traps of the antenna are made from grey covered PVC and painted to produce a minimal visual impact - as far as possible for an antenna! As a minimum, The TZ-WD-1520 should be mounted at least 8m above the ground. Most regulations in Australia permit a mast to be erected 3m above the tallest point of the building (primarily intended for TV antennas) but this ruling can effectively be used to get your ham antenna up at least 8m.

The ground space required for the antenna in an inverted vee configuration is slightly less, and only one support is required. For such an installation, a single support 8 - 10m above ground with the "tails" of the antenna 3 - 4m above ground and separated by about 6 - 8m is ideal. If your block is not large enough to support the antenna elements in a straight line, the element may be bent almost at right angles to a configuration that suits your block shape and size. VSWR may deteriorate in this instance but a tuner may be used and the antenna radiation pattern and efficiency will not be greatly effected.

Ensure that the feedline from the balun is dropped vertically from the feedpoint for at least 5m before being brought of to run to your shack. Ideally, the feedline should be run vertically downwards until it touches the ground to reduce the probability of undesired feedline currents and radiation. This helps to reduce or prevent TVI.

Note that due to the proximity of the ground, end effect, etc, the VSWR dip point of the antenna will vary with the configuration selected and the height above ground. This is a matter of physics! Anyone who tells you otherwise does not know what they are talking about. Changing the height above ground or angle of the Vee can improve or degrade the VSWR or resonant frequency of the antenna. Each installation will be slightly different and yield slightly different results

ANTENNA DESIGN AND COMPONENTS

The TZ-WD-1520 uses 2 coaxial traps which are not affected by rain since the traps are sealed. The traps are coaxial types which offer excellent isolation at the trap frequency.

Stainless steel fasteners are used throughout. The Rippletech TZ-1840 balun is supplied with this antenna. There is no need to purchase a separate balun, and Rippletech never encourages feeding a balanced antenna using coaxial cable without a balun installed. Note some suppliers, quote and supply antennas without a balun (only an insulating block and UHF style SO-259). Make no mistake, use a balun and get optimum performance from your antenna system

PORTABLE OPERATION

The TZ-WD-1520 is also a fantastic antenna for portable operation. Tied between two trees a suitable distance apart, or slung from a high bough in an inverted Vee configuration will yield excellent results, with a minimum of effort.

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